MOTORISTS should switch on their air-conditioning units once a week, 52 weeks of the year to avoid the build up of unpleasant odours.

Research by car care company, Comma, showed more than a third of all motorists admit to never using their air con outside of the summer months.

If it is not used throughout the year it can become a breeding ground for Sick Car Syndrome, triggering fungal spores like Cladosporium and Aspergillus.

Mike Bewsey, spokesperson for Comma, said: “Most people associate air con with summer, but it is equally important to use during the colder months.

“Once established, the bacterial spores quickly multiply to deliver a rather nasty, lingering smell in the car, something buyers of used cars will instantly recognise.”